The present invention relates generally to large area lighting systems, and more particularly to a series connected large area organic light emitting devices.
Organic electroluminescent devices, such as organic light emitting diodes (OLEDs), may be used in a number of applications, including display applications, signage applications and general lighting applications. An OLED device includes one or more organic light emitting layers (“active layers”) disposed between two electrodes, e.g., a cathode and a light transmissive anode, formed on a light transmissive substrate. The active layer(s) emits light upon application of a voltage across the anode and cathode. More specifically, upon application of a voltage from a voltage source, electrons are directly injected into the active organic layer from the cathode, and holes are directly injected into the organic layer from the anode. The electrons and the holes travel through the active organic layer until they recombine at a luminescent center. This recombination process results in the emission of a photon, i.e., light.
Large area OLED devices typically combine many individual OLED devices on a single substrate or a combination of substrates with multiple individual OLED devices on each substrate. Groups of OLED devices are typically coupled in series and/or parallel to create an array of OLED devices which may be employed in display, signage or lighting applications, for instance. For these large area applications, it is desirable to create large light emitting areas in the array while minimizing the areas that do not produce light. Limitations in fabrication technology, as well as issues relating to the interconnection of the OLED devices in the array, provide a number of design challenges.
It is desirable to have a fabrication method, which enables the fabrication of low cost and highly efficient large-area devices.